As semiconductor integrated circuit technology progresses, circuit designers are continually striving to improve circuit performance. One enhancement that can significantly improve circuit performance is increasing of circuit speed. Circuit speed can be increased by improving interconnections between components and/or chips. Traditionally, conventional wiring has been used for such interconnections. Disadvantages commonly associated with conventional wiring schemes include excessive noise, significant delay time, crosstalk, etc. These disadvantages can adversely affect circuit speed, and thus must be taken into consideration by an integrated circuit designer when attempting to optimize circuit speed by improving interconnections.
An alternative to conventional wiring is optical interconnects. Many of the disadvantages associated with conventional wiring do not exist with optical interconnects, and thus optical interconnects can increase circuit speed. Accordingly, utilization of optical interconnects can be attractive for circuit designers seeking to enhance and improve semiconductor circuit performance.
Optical interconnects have previously been implemented with direct bandgap material in Group III-V semiconductor technology, particularly gallium arsenide based technology. As a matter of fact, in GaAs based technology, use of optical interconnects is well known and commonplace, and has been proven to operate faster and function more effectively than wires, by eliminating the above-outlined problems associated with wires. In this regard, it has been demonstrated in GaAs based technology that direct bandgap material can be readily made to lase or emit light for forming optical interconnects.
However, in contrast to direct bandgap material in Group III-V semiconductor technology, optical interconnects are not as readily implemented with indirect bandgap material in Group IV semiconductor technology, particularly silicon based technology, bipolar or CMOS. Since indirect bandgap material does not ordinarily emit light, it is especially difficult to build a light emitting device or optical interconnect from such material.
Specifically, since it is apparent that two-dimensional Si--Ge quantum wells have no light emission capability, one-dimensional or quantum dots (zero-dimensional) are required in a Si--Ge based technology. See, for example, "Quantum Dots of Ge Embedded in SiO.sub.2 Thin Films: Optical Properties", by M. Fujii, S. Hayashi and K. Yamanoto, 20th International Conference on the Physics of Semiconductors, Vol. 3, pp 2375-2378 (1990), which discusses luminescence from microcrystallites of Ge embedded in SiO.sub.2, indicating the existence of quantum dots.
Since silicon is the primary material used in present day semiconductor technology, any enhancement, such as interconnection improvement, that will improve circuit speed in silicon semiconductor technology is highly desirable. Accordingly, a need exists for optical interconnects, and thus light emitting/detecting devices, in silicon based semiconductor technology.